Field of the Invention
The present invention relates to a drive transmission device provided in an image forming apparatus such as a copier or a printer.
Description of the Related Art
Conventionally, in an in-line-type color image forming apparatus which uses an electrophotographic system, for example, a method of controlling respective rotation of an electrophotographic photosensitive member (a photosensitive member) and a developing apparatus separately to suppress the rotation of the developing apparatus as much as possible has been considered in order to obviate problems relating to consumption or deterioration of developer. Moreover, a method in which a photosensitive member and a developing apparatus are driven by one motor and a clutch is provided in a driving system of the developing apparatus to control rotation or a state of stoppage has been considered in order to reduce the cost and the size of an image forming apparatus. A driving system of a developing apparatus of a conventional image forming apparatus often uses an electromagnetic clutch or a spring clutch. However, this configuration has problems in that the cost is relatively high, the shape is limited, malfunction due to slip may occur, etc.
In this respect, Japanese Patent Application Publication No. 2003-208024 discloses a mechanical clutch which is provided in a driving system of a developing apparatus. As illustrated in FIG. 11, this mechanical clutch is configured so that a release member 155 having a cam surface 155c that engages with a cam surface 156c of a clutch lever 156 moves in an axial direction in accordance with the rotation of the clutch lever 156. With movement of the release member 155, a driving-side engagement member 153 is moved in the axial direction, whereby driving is connected and disconnected between a driving-side engagement member 153 and a driven-side engagement member 154. The driving-side engagement member 153 is biased in the axial direction by a coil spring 152 toward a position where engagement with the driven-side engagement member 154 is made possible. When the release member 155 is moved in the axial direction by rotation of the clutch lever 156, the driving-side engagement member 153 moves in the axial direction by the power of the coil spring 152 so as to be connected to the driven-side engagement member 154.
In this mechanical clutch, when realizing the connection, in order to allow the driving-side engagement member 153 and the driven-side engagement member 154 to reliably engage with each other, it is necessary to move the driving-side engagement member 153 toward the driven-side engagement member 154 as quickly as possible. For this purpose, the gradient of the cam surface needs to be set in a manner such as to make inclination surfaces of the cam surfaces 155c and 156c as steep as possible, which means to achieve an increase in the moving amount of the driving-side engagement member 153 in the axial direction in relation to a rotation amount of the clutch lever 156.
However, this mechanical clutch has the following problems to be alleviated. In the mechanical clutch, a state in which the apexes of the cams of the release member and the clutch lever are in contact with each other in the axial direction, which is the moving direction of the release member, is a state in which the connection of driving is released. When the clutch lever is rotated from this state to realize a connection state of driving, the release member moves in the axial direction along the cam surface by the biasing power of the coil spring.
Due to this, when the cam surface is provided at a steep angle to reliably connect the clutch, collision between the release member and the clutch lever occurs and outbreak noise is generated. In recent years, since noise-reduction of an image forming apparatus has progressed, the outbreak noise generated from the mechanical clutch has become increasingly noticeable.